Bioguided isolation, structure elucidation and evaluation of new antimicrobial flavonoid from Carica papaya leaves

Abstract

The emergence of antimicrobial resistance is a global concern, particularly in developing countries. The aims of this study were to isolate and identify antimicrobial fractions of C. papaya based on their antimicrobial activity and evaluate the antimicrobial effects of flavonoid to provide natural resources against S. enteretidis, S. typhi, E. coli, S. flexneri and K. pneumonia using the broth microdilution method. The aqueous fraction showed high inhibition potentials against all the tested bacteria with a Minimum Inhibitory Concentration value of 500 µg/mL. Subsequent phytochemical investigation of aqueous fraction by bioactive-guided column chromatography identified by 1H NMR, 13C NMR and ESI-MS experiments, one new flavonoid named 6"-O-acetyl-3'-O-methyl orientin. The antimicrobial effects of flavonoid against the same pathogens were close to those of the aqueous fraction. This result showed that 6"-O-acetyl-3'-O- methyl orientin is responsible for the antimicrobial activity of Carica papaya leaves and may be considered as antimicrobial lead compound.